Image analysis method, camera and image capturing system thereof

ABSTRACT

An image analysis method is applied to estimating a mounting position of a camera and includes utilizing the camera to capture an image toward a target region. The image includes at least one object of interest. The object of interest has a pixel height in the image. The image analysis method further includes obtaining an inclining angle and a rolling angle of the camera relative to the target region, calculating a mounting height of the camera relative to the target region according to an input height and the pixel height of the object of interest, an image capturing parameter of the camera, the inclining angle and the rolling angle, and performing video content analysis on the image according to the image capturing parameter, the inclining angle, the rolling angle and the mounting height of the camera.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an image analysis method, a camera andan image capturing system thereof, and more specifically, to an imageanalysis method, a camera and an image capturing system thereof forestimating a mounting position of a camera.

2. Description of the Prior Art

In general, a surveillance camera is usually mounted on a high place(e.g. an external wall of a tall building) to capture images toward atarget region and then perform video content analysis (VCA) on thecaptured images for subsequent image surveillance application (e.g.pedestrian or vehicle traffic statistics). However, it is not easy toobtain practical mounting parameters (e.g. a mounting height, a verticalrolling angle and a horizontal rolling angle of the surveillance camerarelative to the target region) of the surveillance camera preciselyduring the mounting process of the surveillance camera. Thus, a largedeviation usually occurs in object identification based on the imagescaptured by the surveillance camera if the position relationship betweenthe surveillance camera and the target region cannot be obtained inadvance. In such a manner, the size and height of an object in thecaptured images cannot be identified correctly. As a result, the priorart usually needs more complicated computation for image identificationand analysis, which greatly increases calculation time of thesurveillance camera in video content analysis so as to considerablyinfluence immediacy and accuracy of the surveillance camera in imagesurveillance application.

SUMMARY OF THE INVENTION

The present invention provides an image analysis method applied toestimating a mounting position of a camera. The image analysis methodincludes utilizing the camera to capture at least one image toward atarget region. The at least one image includes at least one object ofinterest. The at least one object of interest has a pixel height in theat least one image. The image analysis method further includes obtainingan inclining angle and a rolling angle of the camera relative to thetarget region, calculating a mounting height of the camera relative tothe target region according to an input height and the pixel height ofthe at least one object of interest, and an image capturing parameter,the inclining angle and the rolling angle of the camera, and performingvideo content analysis on the at least one image according to the imagecapturing parameter, the inclining angle, the rolling angle and themounting height of the camera.

The present invention further provides a camera including an imagecapturing module, an angle calculation module, and an image analysismodule. The image capturing module captures at least one image toward atarget region. The at least one image includes at least one object ofinterest. The at least one object of interest has a pixel height in theat least one image. The angle calculation module is electricallyconnected to the image capturing module. The angle calculation moduleobtains an inclining angle and a rolling angle of the image capturingmodule relative to the target region. The image analysis module iselectrically connected to the image capturing module and the anglecalculation module. The image analysis module calculates a mountingheight of the image capturing module relative to the target regionaccording to an input height and the pixel height of each object ofinterest, and an image capturing parameter, the inclining angle and therolling angle of the image capturing module. The image analysis moduleperforms video content analysis on the at least one image according tothe image capturing parameter, the inclining angle, the rolling angleand the mounting height of the image capturing module.

The present invention further provides an image capturing systemincluding a camera, an image capturing device, and an image analysisdevice. The camera captures at least one image toward a target region.The at least one image includes at least one object of interest. The atleast one object of interest has a pixel height in the at least oneimage. The angle calculation device is electrically connected to thecamera. The angle calculation device obtains an inclining angle and arolling angle of the camera relative to the target region. The imageanalysis device is electrically connected to the camera and the anglecalculation device. The image analysis device calculates a mountingheight of the camera relative to the target region according to an inputheight and the pixel height of each object of interest, and an imagecapturing parameter, the inclining angle and the rolling angle of thecamera. The image analysis device performs video content analysis on theat least one image according to the image capturing parameter, theinclining angle, the rolling angle and the mounting height of thecamera.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a camera capturing images toward a target regionaccording to an embodiment of the present invention.

FIG. 2 is a functional block diagram of the camera in FIG. 1.

FIG. 3 is a flowchart of an image analysis method according to anembodiment of the present invention.

FIG. 4 is a diagram of an image captured by the camera in FIG. 1 towardthe target region.

FIG. 5 is an enlarged diagram of an object of interest in the image inFIG. 4.

FIG. 6 is a functional block diagram of an image capturing systemaccording to another embodiment of the present invention.

DETAILED DESCRIPTION

Please refer to FIG. 1 and FIG. 2. FIG. 1 is a diagram of a camera 10capturing images toward a target region 11 according to an embodiment ofthe present invention. FIG. 2 is a functional block diagram of thecamera 10 in FIG. 1. As shown in FIG. 1 and FIG. 2, the camera 10 ispreferably an image surveillance apparatus (e.g. IP camera, but notlimited thereto). The camera 10 includes an image capturing module 12,an angle calculation module 14, and an image analysis module 16. Theimage capturing module 12 is used for capturing images toward the targetregion 11 (e.g. a sidewalk). The angle calculation module 14 ishardware, software or firmware (could be directly built in the camera10, but not limited thereto) used for calculating the incliningcondition of the image capturing module 12. The angle calculation module14 is electrically connected to the image capturing module 12 forobtaining an inclining angle α and a rolling angle β of the imagecapturing module 12 relative to the target region 11 as shown in FIG. 1and FIG. 2. The inclining angle α is used for defining the vertical tiltdegree of the image capturing module 12 relative to the target region11. For example, if the inclining angle α is equal to 90°, it representsan image capturing axis L of the image capturing module 12 issubstantially parallel to the target region 11. On the contrary, if theinclining angle α is not equal to 90°, it represents the image capturingaxis L of the image capturing module 12 is tilted upward or downwardrelative to the target region 11. The rolling angle β is used fordefining the horizontal rolling degree of the image capturing module 12relative to the target region 11 as the image capturing module 12 takesthe image capturing axis L as a rotating axis. For example, if therolling angle β is equal to 0°, it represents the image capturing module12 does not roll horizontally relative to the target region 11. On thecontrary, if the rolling angle β is not equal to 0°, it represents theimage capturing module 12 rolls leftward or rightward relative to thetarget region 11.

The image analysis module 16 is hardware, software or firmware (could bedirectly built in the camera 10, but not limited thereto) used forperforming image identification analysis on an image captured by theimage capturing module 12. The image analysis module 16 is electricallyconnected to the image capturing module 12 and the angle calculationmodule 14 for calculating a mounting height H of the image capturingmodule 12 as shown in FIG. 1 and FIG. 2 according to a pixel height andan input height of an object of interest in the image and an imagecapturing parameter, the inclining angle α and the rolling angle β ofthe image capturing module 12. The image analysis module 16 is furtherused for performing video content analysis (e.g. pedestrian or vehicletraffic statistics or video event tracking) on the image captured by theimage capturing module 12 according to the image capturing parameter,the inclining angle α, the rolling angle β, and the mounting height H ofthe image capturing module 12. To be noted, the image capturingparameter includes related image forming parameters (could be systemdefault parameters of the image capturing module 12) set in the imagecapturing module 12 for subsequent angle calculation references of theangle calculation module 14. In this embodiment, the image capturingparameter could preferably include at least one of a focal-lengthparameter, a principal-point parameter and a distortion-coefficientparameter, which means type of image capturing parameter adopted by theangle calculation module 14 could be varied according to the practicalapplication of the camera 10. For example, if the image capturing module12 utilizes a fisheye lens to capture images, image distortion occurs inthe images captured by the image capturing module 12. In this condition,the angle calculation module 14 takes the distortion-coefficientparameter into consideration during the angle calculation process forthe image capturing module 12, so as to improve calculation accuracy ofthe inclining angle α and the rolling angle β.

The image analysis method performed by the camera 10 is described asfollows. Please refer to FIGS. 1-5. FIG. 3 is a flowchart of the imageanalysis method according to an embodiment of the present invention.FIG. 4 is a diagram of an image 13 captured by the camera 10 in FIG. 1toward the target region 11. FIG. 5 is an enlarged diagram of an objectof interest 15 in the image 13 in FIG. 4. The image analysis method ofthe present invention includes the following steps.

Step 300: The image capturing module 12 captures the image 13 toward thetarget region 11.

Step 302: The angle calculation module 14 obtains the inclining angle αand the rolling angle β of the image capturing module 12 relative to thetarget region 11.

Step 304: The image analysis module 16 calculates the mounting height Hof the image capturing module 12 according to a pixel height and aninput height of an object of interest in the image 13 and the imagecapturing parameter, the inclining angle α and the rolling angle β ofthe image capturing module 12.

Step 306: The image analysis module 16 performs video content analysison the image 13 according to the image capturing parameter, theinclining angle α, the rolling angle β and the mounting height H of theimage capturing module 12.

More detailed description for the aforesaid steps is provided as followsin the condition that the image 13 captured by the image capturingmodule 12 has a plurality of objects of interest (i.e. objects ofinterest 15 and 21 as shown in FIG. 4, but not limited thereto). As forthe image analysis process for other objects of interest (not shown inFIG. 4) in the image 13 and other images captured by the image capturingmodule 12, the related description could be reasoned by analogyaccording to the following description and omitted herein.

In Step 300, the image capturing module 12 captures the image 13 asshown in FIG. 4 toward the target region 11, and the objects of interest15 and 21 could have corresponding pixel heights respectively in theimage 13. In Step 302, the angle calculation module 14 obtains theinclining angle α and the rolling angle β of the image capturing module12 relative to the target region 11. To be more specific, in thisembodiment, the angle calculation module 14 could calculate theinclining angle α and the rolling angle β preferably by a method ofestablishing a representative vertical line in an object of interest inan image. For example, the angle calculation module 14 could obtain amark of the object of interest 15 in the image 13 according to aconventional image identification method, such as adopting a neuralnetwork algorithm to identify a representative frame 19 of the object ofinterest 15 as shown in FIG. 5 in the image 13 or adopting aconventional contour identification method to obtain terminal contours(e.g. head and foot contours) of the object of interest 15, forsubsequent representative line calculation. As for the relateddescription for adopting an image identification method to obtain a markof an object of interest for establishing a representative vertical linein an object of interest, it could be commonly seen in the prior art andomitted herein.

After obtaining the marks of the objects of interest 15 and 21 in theimage 13, as shown in FIG. 4 and FIG. 5, the angle calculation module 14establishes a representative vertical line 17 in the object of interest15 and a representative vertical line 23 in the object of interest 21.Subsequently, the angle calculation module 14 calculates anintersection-point coordinate of the representative vertical line 17 andthe representative vertical line 23, which could be regarded as anestimated mounting position of the image capturing module 12. In such amanner, the angle calculation module 14 calculates the inclining angle αand the rolling angle β according to the aforesaid intersection-pointcoordinate and focal-length and principal-point coordinates (could becalculated by the aforesaid image capturing parameter) of the imagecapturing module 12. To be further specific, according to practicalexperimental experience and related equation derivation, the anglecalculation module 14 could preferably adopt the following equations toobtain the inclining angle α and the rolling angle β of the imagecapturing module 12.

the inclining angle α=tan⁻¹{[(V _(x) −C _(x))*f _(y)]/[(V _(y) −C_(y))*f _(x)]};

the rolling angle β=tan⁻¹{[(V _(y) −C _(y))/cos(α)]*f _(y)]};

-   -   wherein (V_(x), V_(y)) is the intersection-point coordinate,        (f_(x), f_(y)) is the focal-length coordinate, (C_(x), C_(y)) is        the principal-point coordinate, and V_(x), V_(y), f_(x), f_(y),        C_(x) and C_(y) are natural numbers (could be positive integers        or negative integers).

In practical application, for improving calculation accuracy of theinclining angle α and the rolling angle β, the angle calculation module14 could calculate the inclining angle α and the rolling angle β furtheraccording to a plurality of intersection-point coordinates generated byrepresentative vertical lines of a plurality of objects of interest. Inbrief, besides the aforesaid objects of interest 15 and 21, the anglecalculation module 14 can establish representative vertical lines ofother objects of interest, and can calculate a plurality ofintersection-point coordinates according to head and tail coordinates ofthe representative vertical line of each object of interest and head andtail coordinates of the representative vertical line of anothercorresponding object of interest. For example, if there are N objects ofinterest in the image 13, the angle calculation module 14 couldcalculate N*(N−1) intersection-point coordinates. Subsequently, theangle calculation module 14 can calculate a plurality of estimatedinclining angles and a plurality of estimated rolling anglesrespectively according to the plurality of intersection-pointcoordinates, the aforesaid focal-length coordinate and the aforesaidprincipal-point coordinate. Finally, the angle calculation module 14preferably adopts the RANSAC (RANdom Sample Consensus) algorithm (therelated description is commonly seen in the prior art and omittedherein) to filter the plurality of estimated inclining angles and theplurality of estimated rolling angles for calculating an optimuminclining angle and an optimum rolling angle, and sets the optimuminclining angle and the optimum rolling angle as the inclining angle αand the rolling angle β respectively. Accordingly, the present inventioncan further improve accuracy of the angle calculation module 14 incalculation of the inclining angle α and the rolling angle β.

After the angle calculation module 14 calculates the inclining angle αand the rolling angle β of the image capturing module 12, the imageanalysis module 16 could utilize the related geometric equations (e.g.trigonometric functions) to calculate the mounting height H of the imagecapturing module 12 according to the pixel height and the input heightof the object of interest 15 (or the object of interest 21) and theimage capturing parameter, the inclining angle α and the rolling angle βof the image capturing module 12. The input height (e.g. an averagepedestrian height, such as 170 cm, but not limited thereto) could bepreferably input by a user. Finally, in the condition that the imageanalysis module 16 has obtained the position relationship between theimage capturing module 12 and the target region 11 (i.e. the incliningangle α, the rolling angle β and the mounting height H of the imagecapturing module 12 as shown in FIG. 1), the image analysis module 16can perform video content analysis on the image 13 according to theimage parameter, the inclining angle α, the rolling angle β, and themounting height H of the image capturing module 12 (Step 306).

In such a manner, via the aforesaid image analysis method, the presentinvention can estimate the practical mounting parameters automaticallyand precisely without inputting the related mounting parameters inadvance (e.g. requesting the user to manually input the inclining angle,the rolling angle, and the mounting height of the image capturing module12 after the mounting process of the camera 10 has been completed) orobtaining the related mounting parameters by a huge and complicatedimage identification process. Thus, the present invention can greatlyreduce the calculation time of the camera in video content analysis soas to efficiently improve immediacy and accuracy of the camera in imagesurveillance application (e.g. pedestrian or vehicle traffic statisticsor video event tracking). Furthermore, even in the condition that azoom-in/zoom-out operation of the camera is performed due to the user'sneeds, the camera can directly perform video content analysis on thezoom-in/zoom-out image according to the zoom-in/zoom-out image capturingparameter, the inclining angle and the rolling angle of the imagecapturing module without recalculation since the practical mountingparameters have been obtained according to the aforesaid image analysismethod and the original image capturing parameter of the image capturingmodule has been known. Accordingly, the present invention canefficiently reduce computation of the camera in video content analysis.

It should be mentioned that the angle calculation module 14 couldfurther calibrate the mounting height H. For example, the anglecalculation module 14 could calibrate the head and tail coordinates ofthe representative vertical line of each object of interest in the image13 according to the calculated mounting height H, the calculatedinclining angle α, the calculated rolling angle β and the imagecapturing parameter, and the angle calculation module 14 can calibratethe plurality of intersection-point coordinates according to thecalibrated head and tail coordinates of each representative verticalline. In such a manner, the angle calculation module 14 can calibratethe inclining angle α and the rolling angle β according to thecalibrated intersection-point coordinates and the focal-lengthcoordinate and the principal-point coordinate of the image capturingmodule 12, and can calibrate the mounting height H according to thepixel height and the input height of each object of interest, the imagecapturing parameter of the image capturing module 12, and the calibratedinclining angle α and the calibrated rolling angle θ, so as to improvethe calculation accuracy of the mounting height H.

Furthermore, if the plurality of objects of interest (e.g. a pedestrianon the sidewalk and a motorcycle rider on the road, but not limitedthereto) in the images captured by the camera 10 belongs to differentheight groups, the image analysis module 16 could divide the aforesaidobjects of interest into different height groups according to aclustering algorithm (e.g. “video object classification with object sizecalibration” disclosed by Saptharishi et al. (US20150093035)).Subsequently, according to a mounting height calculated from the objectsof interest in one of the height groups, the image analysis module 16could estimate a practical height of the object of interest in anotherof the height groups.

For example, after the mounting height H of the image capturing module12 is calculated according to the pixel heights and the input heights ofthe objects of interest 15 and 21 (belong to the pedestrian heightgroup) in the image 13 and the image capturing parameter, the incliningangle α and the rolling angle β of the image capturing module 12, theimage analysis module 16 could perform video content analysis on theimage 13 according to the pixel height of the object of interest in therider height group and the image capturing parameter, the incliningangle α, the rolling angle β, and the mounting height H of the imagecapturing module 12, so as to estimate the practical height of theobject of interest in the rider height group. As for other derivedembodiments, such as the embodiment in which the practical height of theobject of interest in another different height group (e.g. a childheight group) is estimated according to the mounting height calculatedfrom the objects of interest in the rider height group, the relateddescription could be reasoned by analogy according to the aforesaidembodiment and omitted herein.

To be noted, the component configuration of the camera for performingthe image analysis method of the prevent invention is not limited to theaforesaid embodiments, meaning that the present invention could adoptthe design that an angle calculation device is externally coupled to thecamera for reducing computation of the camera. For example, as shown inFIG. 6, which is a functional block diagram of an image capturing system100 according to another embodiment of the present invention, the imagecapturing system 100 could include a camera 102, an angle calculationdevice 104 and an image analysis device 106. The camera 102 is used forcapturing images toward a target region. The angle calculation device104 (e.g. a video control host externally coupled to the camera 102) iselectrically connected to the camera 102 for obtaining an incliningangle and a rolling angle of the camera relative to the target region.The image analysis device 106 (could be internally built in the camera102 or externally coupled to the camera 102) is electrically connectedto the camera 102 and the angle calculation device 104. The imageanalysis device 106 is used for calculating a mounting height of thecamera 102 according to a pixel height and an input height of an objectof interest in an image captured by the camera 102, an image capturingparameter of the camera 102, an inclining angle and a rolling angle ofthe camera 102. The image analysis device 106 is further used forperforming video content analysis on the image according to the imagecapturing parameter, the inclining angle, the rolling angle and themounting height of the camera. The detailed description for thisembodiment could be reasoned by analogy according to the aforesaidembodiments and omitted herein.

Moreover, the step of obtaining the inclining angle and the rollingangle of the image capturing module relative to the target region is notlimited to the aforesaid embodiments, meaning that the present inventioncould utilize an accelerometer to directly obtain the inclining angleand the rolling angle of the image capturing module in anotherembodiment. In brief, in another embodiment, the angle calculationmodule is an accelerometer (could be externally connected to orinternally built in the camera). Accordingly, the angle calculationmodule could directly detect the inclining angle and the rolling angleof the image capturing module without the aforesaid calculation for theinclining angle and the rolling angle, so as to reduce computation ofthe camera when performing the image analysis method of the presentinvention.

In practical application, the present invention could further adopt thedesign of setting a region of interest in the image for reducingcomputation of the camera. For example, in another embodiment, beforethe step of calculating the mounting height of the image capturingmodule is performed, the region of interest could be set in the image(e.g. manually circling the region of interest in the image, such as asidewalk). Accordingly, the image analysis module could calculate themounting height of the image capturing module only according to thepixel height and the input height of each object of interest in theregion of interest, the image capturing parameter of the image capturingmodule, and the inclining angle and the rolling angle of the imagecapturing module, so as to further reduce computation of the camera invideo content analysis.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. An image analysis method applied to estimating amounting position of a camera, the image analysis method comprising:utilizing the camera to capture at least one image toward a targetregion, the at least one image comprising at least one object ofinterest, the at least one object of interest having a pixel height inthe at least one image; obtaining an inclining angle and a rolling angleof the camera relative to the target region; calculating a mountingheight of the camera relative to the target region according to an inputheight and the pixel height of the at least one object of interest, andan image capturing parameter, the inclining angle and the rolling angleof the camera; and performing video content analysis on the at least oneimage according to the image capturing parameter, the inclining angle,the rolling angle and the mounting height of the camera.
 2. The imageanalysis method of claim 1, wherein the image capturing parametercomprises at least one of a focal-length parameter, a principal-pointparameter and a distortion-coefficient parameter.
 3. The image analysismethod of claim 1, wherein the step of obtaining the inclining angle andthe rolling angle of the camera relative to the target region comprises:utilizing an accelerometer to obtain the inclining angle and the rollingangle of the camera relative to the target region.
 4. The image analysismethod of claim 1, wherein the step of obtaining the inclining angle andthe rolling angle of the camera relative to the target region comprises:establishing a representative vertical line of each object of interestin the at least one image; calculating a plurality of intersection-pointcoordinates according to head and tail coordinates of the representativevertical line of each object of interest and head and tail coordinatesof a representative vertical line of another object of interest;calculating a plurality of estimated inclining angles and a plurality ofestimated rolling angles according to the plurality ofintersection-point coordinates, a focal-length coordinate of the camera,and a principal-point coordinate of the camera; calculating an optimuminclining angle and an optimum rolling angle according to the pluralityof estimated inclining angles and the plurality of estimated rollingangles; and setting the optimum inclining angle and the optimum rollingangle as the inclining angle and the rolling angle of the camerarespectively.
 5. The image analysis method of claim 4, wherein the imageanalysis method obtains a mark of each object of interest in the atleast one image according to a neural network algorithm and calculatesthe head and tail coordinates of the representative vertical line ofeach object of interest according to the image capturing parameter andthe mark of each object of interest.
 6. The image analysis method ofclaim 4, wherein the intersection-point coordinate is (V_(x), V_(y)),the focal-length coordinate is (f_(x), f_(y)), the principal-pointcoordinate is (C_(x), C_(y)), and the inclining angle and the rollingangle are calculated according to the following equations:the inclining angle=tan⁻¹{[(V _(x) −C _(x))*f _(y)]/[(V _(y) −C _(y))*f_(x)]};the rolling angle=tan⁻¹{[(V _(y) −C _(y))/cos(α)]*f _(y)]}; whereinV_(x), V_(y), f_(x), f_(y), C_(x) and C_(y) are natural numbers.
 7. Theimage analysis method of claim 4, wherein the image analysis methodfilters the plurality of estimated inclining angles and the plurality ofestimated rolling angles according to the RANSAC (RANdom SampleConsensus) algorithm to calculate the optimum inclining angle and theoptimum rolling angle.
 8. The image analysis method of claim 4 furthercomprising: calibrating the head and tail coordinates of therepresentative vertical line of each object of interest according to themounting height, the inclining angle, the rolling angle and the imagecapturing parameter; calibrating the plurality of intersection-pointcoordinates according to the head and tail coordinates of eachrepresentative vertical line and the head and tail coordinates ofanother representative vertical line after being calibrated; calibratingthe inclining angle and the rolling angle according to the plurality ofintersection-point coordinates after being calibrated and thefocal-length coordinate and the principal-point coordinate of thecamera; and calibrating the mounting height according to the pixelheight and the input height of each object of interest, the imagecapturing parameter of the camera, and the inclining angle and therolling angle after being calibrated.
 9. The image analysis method ofclaim 1, wherein the at least one image further comprises at least oneanother object of interest, the at least one another object of interesthas another pixel height in the at least one image, and the imageanalysis method further comprises: dividing the at least one object ofinterest and the at least one another object of interest into at leasttwo height groups according to a clustering algorithm; and performingvideo content analysis on the at least one image according to the pixelheight of the at least one another object of interest, the imagecapturing parameter, the inclining angle and the rolling angle of thecamera, and the mounting height calculated according to the at least oneobject of interest corresponding to one height group, to estimate apractical height of the at least one another object of interestcorresponding to the other height group.
 10. The image analysis methodof claim 1, wherein the step of calculating the mounting height of thecamera comprises: setting a region of interest in the image; andcalculating the mounting height of the camera according to the pixelheight and input height of each object of interest in the region ofinterest, the image capturing parameter of the camera, and the incliningangle and the rolling angle of the camera.
 11. A camera comprising: animage capturing module capturing at least one image toward a targetregion, the at least one image comprising at least one object ofinterest, the at least one object of interest having a pixel height inthe at least one image; an angle calculation module electricallyconnected to the image capturing module, the angle calculation moduleobtaining an inclining angle and a rolling angle of the image capturingmodule relative to the target region; and an image analysis moduleelectrically connected to the image capturing module and the anglecalculation module, the image analysis module calculating a mountingheight of the image capturing module relative to the target regionaccording to an input height and the pixel height of each object ofinterest, and an image capturing parameter, the inclining angle and therolling angle of the image capturing module, and the image analysismodule performing video content analysis on the at least one imageaccording to the image capturing parameter, the inclining angle, therolling angle and the mounting height of the image capturing module. 12.An image capturing system comprising: a camera capturing at least oneimage toward a target region, the at least one image comprising at leastone object of interest, the at least one object of interest having apixel height in the at least one image; an angle calculation deviceelectrically connected to the camera, the angle calculation deviceobtaining an inclining angle and a rolling angle of the camera relativeto the target region; and an image analysis device electricallyconnected to the camera and the angle calculation device, the imageanalysis device calculating a mounting height of the camera relative tothe target region according to an input height and the pixel height ofeach object of interest, and an image capturing parameter, the incliningangle and the rolling angle of the camera, and the image analysis deviceperforming video content analysis on the at least one image according tothe image capturing parameter, the inclining angle, the rolling angleand the mounting height of the camera.